ABSTRACT
Abstract. The high order harmonic emission in atoms driven by intense femto-second laser pulses can lead to a single atto-second XUV pulse or an atto-second XUV pulse train in which the pulse period is half of the fundamental laser period, depended on the driving pulse duration and the pulse's carrier-envelop phase (CEP). The driving laser field assisted attosecond XUV photo-ionization was used successfully to measure the duration of the atto-second pulse based on the cross-correlation method. However, this method in principle can not tell single atto-second pulse from atto-second pulse train. In this paper, we propose a technique for directly telling single atto-second pulse from atto-second pulse train based on the photo-ionization of atoms by the atto-second XUV pulse in the presence of two-color strong laser pulse.
